A Soft-Real-Time-Optimal Semi-Clustered Scheduler with a Constant Tardiness Bound

Different global and semi-partitioned schedulers have been proposed that are soft-real-time (SRT) optimal for sporadic task systems, meaning they can guarantee bounded deadline tardiness. However, under known analyses, tardiness bounds increase with respect to the number of processors, which reduces the applicability of these schedulers in systems with a large number of processors. In this paper, a semi-clustered scheduler, SC-EDF, is presented that has a constant tardiness bound. SC-EDF partitions tasks into clusters, each of which may include one fractional processor. Each cluster is scheduled by G-EDF, and the fractional processors are realized using Pfair scheduling techniques.